The Liquid Crystal Display (LCD) is the most widely used display product in the present market. The production technology is quite mature. The yield of the production is high. The production cost is relatively low and the acceptance is high in the market. Most of the liquid crystal displays on the present market are backlight type liquid crystal display devices, which comprise a liquid crystal display panel and a backlight module. Generally, the liquid crystal display panel comprises a color filter (CF) substrate, an array substrate, liquid crystal and a sealant sandwiched between the color filter substrate and the array substrate. The CF substrate mainly includes a color filter layer for forming colored lights with color resist units (R/G/B), a black matrix (BM) for preventing light leakage from the pixel edge, and photo spacers (PS) for maintaining a cell thickness. In a large scale liquid crystal display panel, more than two types of photo spacers are commonly used. As an illustration, a main photo spacer (Main PS) and a sub spacer (Sub PS) are provided on a CF substrate to play a role of multi-stage buffering for avoiding the occurrences of kinds of Muras or undesirable phenomena.
The black photo spacer (BPS) material is a new type of material that does not only have the characteristics of the spacer material of the prior art, such as superior elastic recovery force and lower pollution to the liquid crystal, but also possesses the properties of the black matrix material, such as a higher optical density (OD) value to provide a light shielding effect. Therefore, it can be used to combine the BM process and the PS process into one to reduce one photolithography process for reducing material cost and tact time, thereby reducing overall production cost.
The COA (Color Filter On Array) technology is to prepare the color filter layer on the array substrate. Since no alignment issue of the color filter substrate and the array substrate exists in the COA display panel, the difficulty of the cell process in the display panel manufacture process can be reduced to prevent the tolerance of the cell process. Accordingly, the black matrix can be designed to be narrow line width for promoting the aperture ratio of the pixel. A new BM-Less technology is a technology based on COA technology that combines BM and PS in the same BPS material and is completed in the same process and designed on the array substrate. Compared with the traditional liquid crystal display technology, the black matrix, the main photo spacer, the sub spacer and the color filter film are all designed on the array substrate side. The light leakage due to the shifting due to the assembly errors in the assembly process or due to the panel bending in the curved surface display. More importantly, one process and the material thereof can be eliminated to shorten the production time and to reduce the production cost.
However, the skill of BPS materials at present is relatively difficult, the mass production has not been achieved, and the price is expensive. In the existing BPS type product structure as shown in FIG. 1, the single layer of the first color resist 201 or the second color resist 202 below the main photo spacer 101 or the sub photo spacer 102 serves as a pad carrier. A height difference between the main photo spacer 101 and the sub photo spacer 102 is formed by a thickness difference between the first color resist 201 and the second color resist 202. The thickness hi of the main photo spacer 101 and the sub photo spacer 102 is similar to the cell gap H1 of the liquid crystal panel. The usage amount of the BPS material for the main photo spacer 101 and the sub photo spacer 102 is relatively large and the cost is high.